I too have a slap chop. I do have a decent amount of knife skill, but sometimes I am flat out lazy and bust out the slap chop. Only drawbacks are the pieces are not quite uniform, and don't try slapping a piece of onion or potato that takes up all the chopping space in the chopper. If you overload it the blade will stick somewhere along the way.
That WS chopper the OP has looks cool and all... But COME ON! Vince didn't promote it! Everybody loves Vince...